Insects, nematodes, and related arthropods annually destroy an estimated 15% of agricultural crops in the United States and even more than that in developing countries. Some of this damage occurs in the soil when plant pathogens, insects and other such soil borne pests attack the seed after planting. In the production of corn, for example, much of the rest of the damage is caused by rootworms—insect pests that feed upon or otherwise damage the plant roots; by cutworms, European corn borers (ECB), and by other pests that feed upon or damage the above ground parts of the plant. General descriptions of the type and mechanisms of attack of pests on agricultural crops are provided by, for example, Metcalf (1962) in Destructive and Useful Insects: Their Habits and Control, Fourth Edition. (Earlier editions by C. L. Metcalf and W. P. Flint) McGraw-Hill Book Company; New York, San Francisco, Toronto, London; and Agrios, (1988) in Plant Pathology, 3rd Ed., Academic Press.
Traditionally, crop rotation and use of insecticides were the primary management strategies for corn rootworm [Western corn rootworm (Diabrotica virgifera virgifera LeConte), Northern corn rootworm (Diabrotica barberi Smith and Diabrotica barberi Lawrence), and Southern corn rootworm (Diabrotica undecimpunctata howardi Barber)] in North America. However, the adaptation of a biotype of Western corn rootworm (WCR) to preferentially lay eggs on soybean plants; the adaptation of a biotype of Northern corn rootworm (NCR) resulting in extended diapause in eggs; counter-resistance of corn rootworms to soil and foliar insecticides; and an increased demand for continuous corn have resulted in significant range expansion of this insect pest in recent years. The commercial availability of rootworm-protected transgenic insecticidal corn hybrids (Bt) has provided an effective alternative, resulting in a rapid increase in acreage of transgenic corn for WCR control. Insect resistance management approaches need to be considered with respect to widespread use of Bt insecticidal proteins. Similar issues and concerns exist with control plans for other insect pests such as European corn borer.
There is a need for additional methods of control that can be used in conjunction with other methods or processes towards a cost-effective and sustainable insect pest management program. There is also a need for methods to reduce the probability of development of resistance towards the Bt toxin in insect pests.